A paint, a printing ink, an adhesive, etc., which are cured by irradiation with an active energy beam such as an electron beam or an ultraviolet light are advantageous over the conventional paint, printing ink, adhesive, etc., which are thermally cured and dried, in that the process speed can be increased, that an environmental problem is not generated because a solvent is not used, and that the energy beam irradiation apparatus can be miniaturized, and, thus, have come to be put to a practical use. In the active energy beam irradiation, the irradiation is carried out in many cases under an inert gas atmosphere, and the irradiation under a reactive gas is also being studied. The irradiation under the inert gas atmosphere will now be described mainly in the following.
Some of the paints, printing inks, adhesives, etc. are subject to a curing inhibition caused by oxygen and fail to be cured unless the irradiation is carried out under an inert gas atmosphere such as a nitrogen gas atmosphere. In such a case, it is necessary to supply an inert gas into the irradiating chamber so as to substitute the inert gas in the irradiating chamber for carrying out the active energy beam irradiation. However, where the object to be irradiated is continuous such as a web, it is impossible to close the object transport inlet and outlet, with the result that the amount of the air entering the irradiating chamber together with the web is increased with increase in the processing speed so as to lower the purity of the inert gas atmosphere within the irradiating chamber. As a result, it is unavoidable to increase the amount of the inert gas used, resulting in a serious problem such as an increase in the running cost.
A measure for overcoming the above-noted problem is proposed in, for example, Japanese Patent Disclosure (Kokai) No. 48-86930. It is proposed that the transport outlet of the irradiating chamber of the object is closed by a nip roll or the like, that an inert gas spurting device and a plurality of partitioned chambers are arranged in the transport inlet, and that a gas discharge pipe is arranged in each of the partitioned chambers so as to prevent the air intrusion. It is taught that the particular technique permits lowering the oxygen concentration within the irradiating chamber to several percent or less.
Another measure is proposed in Japanese Patent Disclosure No. 5-60899. It is proposed that a plurality of nozzles for blowing an inert gas against the surface of the target object to be irradiated and a transport duct covering at least partially the roll for guiding the transport of the target object are arranged along the transport passageway of the target object. It is taught that the particular technique permits increasing the utilization rate of the inert gas for forming an inert gas atmosphere in the irradiating region.
Another measure is proposed in Japanese Patent Disclosure No. 60-90762. It is proposed that an inert gas supply section is arranged within the irradiating chamber having the transport inlet sealed with a cylinder of a printing machine and the transport outlet sealed with a pair of rolls, and that a gas discharge section is arranged in the vicinity of the irradiating chamber. It is taught that the particular technique permits decreasing the amount of the inert gas used and also permits a high speed processing.
A still another measure is proposed in Japanese Patent Disclosure No. 9-138300. It is proposed that a transport roll is arranged in the transport inlet so as to narrow the opening, thereby suppressing the supply of the inert gas. It is also taught that it is possible to prevent the fluttering generated along the flow of the target object that is transported continuously.
In the conventional constructions described above, however, it is necessary supply the inert gas to the inert gas spurting nozzles arranged on one or both sides of the irradiating chamber as well as into the irradiating chamber, leading to an increase in the total amount of the inert gas used.
In the case of arranging a gas discharge pipe, it is necessary to control appropriately the atmosphere within the irradiating chamber. However, it is difficult to have the supply amount of the inert gas and the gas discharge amount balanced. Where the supply amount and the discharge amount are markedly unbalanced, a problem is generated that the amount of the inert gas used is increased. Also, where the inert gas having a high flowing speed is spurted from the inert gas spurting nozzle, a negative pressure is established in the vicinity of the nozzle so as to suck the air from the transport inlet and outlet and from the clearance around the irradiating chamber, giving rise to the problem that the oxygen concentration is not lowered to a desired level. In addition, in the apparatus in which a cover is not mounted to the roll, the inert gas leakage takes place in a large amount.
Further, if the inert gas supply section and the gas discharge section are arranged and, particularly, made integral with a printing machine, or if a partitioned chamber is arranged in front of the irradiating chamber, the entire apparatus is rendered bulky. Naturally, the inner volume of the apparatus is increased, resulting in failure to decrease the amount of the inert gas used. Where the transport inlet is sealed by the cylinder of a printing machine, it is necessary to arrange the printing machine and the active energy beam irradiating apparatus as a set. However, it is practically difficult to add an active energy beam irradiating apparatus to the printing machine arranged in advance.
What should be noted is that, in the conventional active energy beam irradiating method and apparatus, measures are certainly taken to increase the gas flow resistance. However, the conventional apparatus and method are irrelevant to the concept of controlling the amount of the gas passing through the transport inlet and outlet. Where the balance of the gas flow resistance is poor, the amount of the inert gas used for forming the inert gas atmosphere was possibly increased.
It should also be noted that, where the atmosphere within the irradiating chamber is held at a negative pressure, the air is sucked in, for example, from the transport inlet and outlet and from the clearance around the irradiating chamber, resulting in failure to substitute an inert gas within the irradiating chamber. In other words, the oxygen concentration within the irradiating chamber fails to be lowered to a desired level.